FR2546454A1 - SELF-PROPELLED WORKING VEHICLE - Google Patents

Abstract

SELF-PROPELLED WORK VEHICLE 1 CONSISTING OF A CHASSIS 2, AN ENGINE 3 MOUNTED ON THIS CHASSIS, A TOOL PROVIDED ON THE CHASSIS, AND CONNECTED TO THE ENGINE TO BE DRIVEN BY IT, A STEP MECHANISM SUSPENDED TO THE CHASSIS OF THE VEHICLE, THE GEAR HAVING AT LEAST ONE DRIVE WHEEL 25 MOUNTED ON AN AXLE 27, A FIRST TRANSMISSION PLACED IN THE CHASSIS, THE FIRST TRANSMISSION HAVING A DRIVE SHAFT 14 EXTENDING IN A FORWARD-REAR DIRECTION OF THE VEHICLE, A DRIVE DISC FIXED AT ITS CENTER AT THE REAR END OF THE DRIVE SHAFT, A DRIVED SHAFT 22 MOUNTED AT THE REAR OF THE DRIVE DISC PERPENDICULARLY TO THE DRIVE SHAFT AND CONNECTED IN OPERATION AT THE DRIVE WHEEL AXLE, AND A FRICTION DISC 31 MOUNTED TO SLIDE ON THE DRIVEN SHAFT 32.

Description

Self-propelled work vehicle.

  The present invention relates to a self-propelled work vehicle and in particular to a self-propelled work vehicle of the type comprising an engine,

  a tool driven by the engine and a wheel or a wheel

motor-driven nille.

  Self-propelled work vehicles are known

  pulses of the type comprising a motor, a tool driven by the motor, and a wheel driven by this motor such as that which is proposed in US Pat. No. 3,580,351

by I J MOLLEN.

  In the US patent of Mollen, the tool takes the form of the combination of a device

  snow collector and snow blower device.

  In other words, the US patent of MOLLEN

  discloses self-propelled work vehicle

  both in the form of a snow-clearing tractor comprising a power transmission system

  shown schematically in Figure 5 which represents

  feels a device of the prior art.

  In FIG. 5, the reference 200 is used to designate the power transmission system. The power transmission system 200 is equipped

  a motor 201 comprising a shaft 202 arranged along the length

  linearly in a direction from the front towards

  the rear of the vehicle Engine power at the exit

  tie of the shaft 202 is transmitted by means of a driving pulley 203 mounted at one end of the shaft 202, via a transmission belt 204 driven by the driving pulley 203, to a pulley driven 205 mounted at the rear end of a shaft 208 serving as the drive shaft of a tool comprising a helical auger 206 and a snow blower 207, which results in the combination of the helical auger 206 and the blower 207 to be used as a tool to remove

the snow.

  In addition, the shaft 202 is provided for in-

  dragging by means of a gear train 209, a tree

  with cam 210 on which is mounted another pulley me-

  belt 211 used to drive another drive belt

  drag 212 The power of the engine collected on the drive belt 212 is transmitted by means of a main transmission 213 to an axle 221 of a driving wheel 222 The main transmission 213, which is mounted longitudinally relative to the vehicle, comprises a drive shaft 214 on the front end of which is mounted a driven pulley 215 driven by the drive belt 212 and at

  the rear end of which is mounted a disc

  drag 216 placed transversely to the

  vehicle and a driven shaft 217 arranged perpendicular

  cularily to the drive shaft 214, namely transversely to the vehicle, the driven shaft 217 comprising, at one of its ends, a friction disc 218 axially slidable, mounted on it and engaged in friction with the drive disc 216 and an output gear 219 is

mounted at its other end.

  The friction disc 218 has on its periphery an elastic ring 223 fixed on it and intended to establish a friction engagement with the drive disc 216, this making it possible to transmit the necessary drive power from the disc 216 to the disc 218 Le gear wheel 222 gear change can be

  carried out in a well known manner, for example in provo-

  first of all removing the drive disc 216 in order to free the friction disc 218 from its

  friction engagement and then moving conve-

  the friction disc along the shaft

  driven 217, before advancing the drive disc

  tra Inement 216 in order to bring the friction disc 218

  again in friction engagement with him.

  However, when an elimination tractor

  snow is moving on the snow which accumulates-

  tion may not be regular depending on the surface of the ground and the snowfall conditions, the load

  in the form of a couple on its main transmission

  blade is subject to variations depending on the

  the amount of snow accumulation, such a variation

  tion can be effectively absorbed by the main transmission which is disc type

  friction as described above.

  Such a snow removal tractor is

  however planned to carry out a work of elimination-

  tion of snow, so that its speed is established beforehand so as to be particularly

  low compared to vehicle speed, that is

  to say that it is as small as the speed of a man's walk, so that the movement back and forth with respect to the place o is effected

work must be very slow.

  To avoid such disadvantages, the main transmission 213 can be first

  modified by enlarging the diameter of the disc

  drag 216 as well as the amplitude of movement of the friction disc 218 Such a modification, however, inevitably leads to an increase in the dimensions of the transmission itself, as well

  than that of the snow removal tractor.

  On this subject, if we take into account the variations of load due to displacement on snow,

  it can be very interesting to use the trans-

  friction disc type mission which can be provided with a relatively simple construction to adapt to the load variation However,

  as the dimension parameters of such trans-

  common type missions are determined to be most effective at very low travel speeds, this implies that any modification such as enlarging the diameter of the drive discs cannot result in anything other than lowering the service life of such a transmission This is due to the fact that the widening of the range of running speeds of snow removal tractors to the extent indicated above, results in a reduction in the ratio of transmission gear, which has

  to subject the corresponding friction disc to

laying to larger couples.

  In other words, it may be considered difficult to increase the range of running speeds of such snow removal tractors without impairing the function inherent in the friction disc type transmission and without increasing its dimensions. On the other hand, as a second possible modification, the interposition of a sub-transmission between the main transmission 213 and the drive wheel 222 can be used to increase the speed range of the snow removal tractor Une however, such interposition again leads to an increase in the reduction in the gear ratio of the power transmission system, as in the case of the above modification, which directly results in the subjection of the main transmission to an inversely proportional increase in torque. increased gear ratio, which is detrimental to

  the duration of the main transmission.

  For this reason also, it can be very difficult to increase the range of running speeds of a common type snow removal tractor having a friction disc type transmission, without prejudice to the duration of the transmission. . The present invention has been implemented to effectively solve such common problems encountered in self-propelled work vehicles and in particular in the case of

snow removal tractors.

  The present invention aims to provide a self-propelled work vehicle comprising a chassis, a motor mounted on this chassis, a tool provided on this chassis and connected to the motor to be driven by it, a walking mechanism suspended from the chassis of the vehicle, the drive mechanism having at least one drive wheel mounted on an axle, a first transmission placed in the chassis, the first transmission having a drive shaft extending in a direction going from the front to the rear of the vehicle, a drive disc fixed in its center to the rear end of the drive shaft, a driven shaft mounted at the rear of the drive disc perpendicular to the drive shaft and connected in operating at the axis of the drive wheel, and a friction disc mounted so as to be able to slide on the driven shaft in a non-rotary manner and fixed on its periphery so as to be able to engage in friction with the disc d training, and a second transmission placed in the chassis of the vehicle, the second transmission being connected in operation to the engine

2546454 -

  and supporting at least the front end of the drive shaft, so that the drive power of the motor can be transmitted to the drive shaft in the form of a transmissible torque in at least two ratios of speeds. Accordingly, the present invention

  aims to provide a self-contained work vehicle

  powered having a friction disc type main transmission allowing its operating speed to increase without giving rise to a

  increase in diameter of the main transmission

  pale and without affecting the duration of the trans-

  mission. Other advantages and characteristics of

  this invention will also emerge from the

  following description given with reference to the accompanying drawings in which:

  Figure 1 is a long sectional view

  schematic tudinal, with representation of the power transmission system, of a self-propelled work vehicle in accordance with the preferred embodiment of the invention; Figure 2 is a schematic top view of an essential part of the self-propelled work vehicle of claim 1;

  Figure 3 is a long sectional view

  enlarged tudinal of a sub-transmission of the self-propelled work vehicle of claim 1; Figure 4 is an enlarged view of the left side of the clamping movement of the power transmission system of Figure 1; Figure 5 is a schematic sectional view comprising the representation of the power transmission system of a snow removal tractor

of current type.

  In FIGS. 1 and 2, the reference has been given

  rence 1 to the self-propelled work vehicle and this

  this is in the form of a snow removal tractor according to the preferred embodiment of the invention in which the manner of extracting the power of the engine as well as transmitting the power of the drive disc by means of a friction disc to a drive wheel is similar to that described

  above about the prior art.

  The snow removal tractor 1 comprises a chassis 2 equipped with an engine 3 and a fuel tank 4 The engine 3 is housed in a box 8

  on chassis 2 and is placed in a longi-

  tudinal going from the front to the rear of the ch & ssis 2, and it has a piston 5 connected by a connecting rod 6 to a shaft 7 The shaft 7 advances towards the front of the boot 8 providing an advanced a pair of pulleys 10, 11 which are mounted on this projection and spaced apart in the axial direction of the shaft 7, the pulleys 10 and 11 being used respectively to drive a working tool which

  will be described below and a drive wheel.

  The chassis 2 comprises a front partition 16 which is placed on its front side and is provided with a blowing enclosure 13, this enclosure 13

  comprising at its lower part a part of

  auger ring 12 open forwards to accommodate

  internally an auger 21 and a snow blower 23.

  serving as tools and in its upper part a conductive part 13 has snow blowing which

  rises forward along a linear curve.

  The snow blower 23 is mounted on a drive shaft

  tool drag 14 placed in the blowing box 31 longitudinally relative to the vehicle, thus extending parallel to the shaft 7 of the motor 3, the drive shaft 14 comprising in its front part, a transmission gear 14 a which is fixed on it and at its rear end a rear extension 17 extending rearwards near the partition 16 In addition, the transmission gear 14 a is designed to be associated with a pinion 22 fixed on a driven shaft 20 which is placed in the cover part 12 of the auger transversely relative to the vehicle and on which the auger is fixed 21 The rear extension 17 of the drive shaft 14 of the tool has at its rear part a driven pulley 18 which is fixed on it and which is driven by a drive belt 19 driven by the

  belt 10 which is fixed on the shaft 7 of the motor 3.

  Incidentally, a partition 16 is provided to separate the blowing chamber 13 and a structure 15 from the

chassis 2.

  In the above arrangement, the auger 21 and the snow blower 23 together with the blowing chamber 13 form a working tool for

  the elimination of snow, the power of which

  is transmitted from the shaft 7 of the motor 3 by means of the drive pulley 10, the drive pulley 19 and the driven pulley 18, to the drive shaft 14 of the tool, which causes the snow blower 23 to rotate and

  then via the transmission gear

  mission 14 a and of the pinion 22, towards the driven shaft 22 by rotating the auger 21 It follows that the snow collected by the auger 21 is directed towards the rear at the bottom of the blowing chamber 13

254645-4

  and is subsequently driven by the rotation of the snow blower 23 to rise into the duct part 13 a and to leave it so that

  the snow is evacuated properly.

  In addition, at the bottom of the structure 15 of the chassis 12, to its left and to its right is provided a pair of walking wheels, supported on a drive axle 27 suspended from the structure 15, the wheels 25, 25 being provided to drive a pair of tracks 24, 24 The tracks 24, 24 can be guided by means of a pair of guide wheels 26, 26 which are each fixed to the outer ends of a guide pin 26 a, the axis 26 a being supported by a part i 5 a carrying an axis and extending backwards being formed

  on the lower rear part of the structure 15.

  With such a displacement mechanism comprising the tracks 24, 24, the snow removal tractor

  is guided non-stop and depending on the circumstances

  tances during its movement and its function

  operation. The drive axis 27 of the walking wheels 25, 25 has in its cover 25 c provided inside the side wall 15 b, the left side wall of this embodiment, of the structure 15, a final pinion 28 fixed on this axis and associated with a pair of guide pulleys 29.30 mounted in the cover 15 c and provided for

be able to rotate together.

  In addition, inside the intermediate rear part of the structure 15 is mounted a friction disc 31 fixed on a driven shaft 32 Rotatable extending transversely relative to the vehicle, this friction disc 31 is keyed on a groove 32 a of the driven shaft 32, so as to slide along a predetermined path but without being able to rotate and has along its periphery to which it is fixed an elastic ring 37, this elastic ring 37 facing the friction disc The driven shaft advances at its corresponding end inside the cover 15c so as to have an output pulley 33 fixed on it, the output pulley 33 being associated with one of the guide pulleys 29, 30 If necessary for changing the speed of the running wheels 25, 25 and consequently of the tracks 24, 24, the friction disc 31

  can slide along the shaft 32 thanks to a mechanism

  displacement not shown, in a well known manner.

  In addition, at the front of the friction disc 31, a drive disc 34 is provided which can rotate in a plane perpendicular to the friction disc 31 and consequently parallel to the driven shaft 32, the drive disc 34 having on its rear side a friction surface 36 which is normally in frictional contact with the elastic ring 37 of the friction disc 31 The drive disc 34 is fixed in its center to the rear end of a shaft drive 35 normally advancing towards the drive disc 34 and perpendicular to the driven shaft 32 and thus parallel to the shaft 7 of the motor 3, the drive shaft 35 advancing rearward outside sub-transmission 38,

  which is placed in the structure 15 for trans-

  put drive power from the shaft 7

to the drive disc 34.

  In Figure 3, we observe that the sub-

  transmission 38 comprises a transmission box 39 consisting of two separable halves front and rear it

  rotating the drive shaft respectively

  35 and an input shaft 57 arranged parallel to the drive shaft 35 The box 39 has at its bottom portion a boss 41 and rotatably mounted on a pivoting shaft 40 arranged transversely to the

  vehicle, the pivoting shaft 40 being fixed to the structure

  ture 15 During operation, the movement mechanism of the friction disc 31, the entire part of the sub-transmission 38 can return to rotation by means of a corresponding mechanism (not shown), in an anti-clockwise direction in the case of FIG. 3 around the pivoting shaft 41,

  so as to disengage the drive disc thereby

  34 relative to the elastic ring 37 of the friction disc 31, before sliding the friction disc 31 along the driven shaft 32 to change the corresponding speed The drive shaft 35 is rotatably supported at its front end by means of a bearing part 44 provided inside an advanced lower part 43

  of boot 39 and on its rear part, in a posi-

  tion slightly advanced from its rear end, by means of a bearing 42 placed at the rear rear part of the box 39 In the box 39, the drive shaft 35 comprises a pinion 45 of large diameter and a pinion 46 of small diameter fixed on it so as to be able to rotate together without sliding along its length, the pinions 45, 46 of large diameter and of small diameter being axially spaced from one another Between the pinions 45, 46 and the shaft drive 35 is formed a groove 47 with a displacement element 48 which can slide axially and keyed thereto, in this displacement element 48 is formed a peripheral annular slot 49 which engages with a displacement fork 50 which can be actuated at by means of a lever 51 controlled

  by a control cable 52 shown in FIG. 1.

  The displacement element 48 is equipped on its rear part with a rear projection 53 and on its front part with a front projection 54 on the one hand and the pinions 45, 46 of large diameter and small diameter are provided with a rear recess 55 on the front face of a first and a front recess 56 on the rear face of the latter on the other hand, so that the displacement element 48 moves by sliding along the shaft drive 35, the projections 53, 54 must each be brought into engagement with one of the corresponding recesses 55, 56, and especially the rear projection 53 and the rear recess 55 as well as the front projection 54 and the recess before 56

constitute a chatter.

  In addition, the input shaft 57 is mounted in parallel with the drive shaft 35 as described above and rotatably supported at its rear end by a bearing portion-59 formed inside of the upper rear part 58 of the boot 39 and on its intermediate part, in a slightly frontal position, by means of a bearing 60 placed on the part

  upper front of box 39, and has an extension

  front bearing 57 a extending at the front of the gearbox 39, on the extension 57 of which is fixed a pulley 61 driven by a drive belt 62 driven by a drive pulley 11 fixed on the shaft 7 of the motor 3 In the box 39, the input shaft 57 comprises a pinion 63 of small diameter and a pinion 64 of large diameter which are fixed on it to be normally associated with the pinions 45, 46

  of large diameter and small-diameter mounted respectively

  vement on the drive shaft 35, the pinions 63, 64 of small diameter and large diameter being spaced

axially from each other.

  In the above arrangement of the sub-trans-

  mission 38, a relatively low speed gear train with a relatively large reduction gear ratio is formed by the pinion 63 of small diameter on the input shaft 57 and by the pinion 45 of large diameter on the drive shaft 35 and a relatively high speed high speed gear train b is formed by the pinion 64 of large diameter on the input shaft 57 and by the pinion 46 of small

  diameter on the drive shaft 35.

  It appears from FIG. 3 that when the pinions 63, 64 on the input shaft 57 are rotated, while the displacement element 48 is placed in an intermediate position between the pinions, 46 on the shaft drive 35, these pinions 45, 46 rotate freely without any restriction, which prevents the drive power as it is

  transmitted to the input shaft 57 to be transmitted equally

drive shaft 35.

  We now describe with reference to

  Figures l and 3 the operation of the transmission system

  power mission, including the sub-transmission 38, of the snow removal tractor 1 during

  the drive of the tracks 24, 24 e.

  In the state shown in Figure 3, the driving force collected at the outlet of the shaft 7

  of motor 3 is transmitted by the drive pulley

  11, the drive belt 62 and the driven pulley 61 towards the input shaft 57, which has the effect of causing the pinions 63, 64 to rotate on the input shaft 57, thus causing the pinions 45, 46 on the drive shaft 35, the pinions 45, 46 being normally associated respectively with the pinions 63, 64, to rotate freely at different speeds In addition, when the displacement fork 50 is brought into

  operation to slide the moving element

  cement 48 to the right of FIG. 3 so that the rear projection 53 of the displacement element 48 is brought to cooperate with the rear recess 55 formed in the pinion 45 of large diameter on the drive shaft 35 , the displacement element 48 rotates integrally with the pinion 45 of large diameter, which has the effect of transmitting the rotation of the pinion 63 of small diameter on the input shaft 57 towards the drive shaft 35, in thereby causing the relatively small speed rotation of the drive disc 34 attached to the rear end of the drive shaft 35 As a result, the friction disc 31 which is normally driven to engage friction with the friction disc 34, is rotated

  with disc 34 thereby transmitting power -

  driven by the driven shaft 32, the output pinion 33, the guide pulleys 29, 30, the final pinion 28 and the drive pin 27, towards the drive wheels

  , 25 thereby driving the tracks 24, 24 indefi-

  niment In the state where the sub-transmission 38 has kept the gear train at low speed, the snow removal tractor moves at a relatively low speed, which means that the movement towards the low speeds of the sub-transmission 38 is suitable for the snow-removing tractor 1

  during snow removal.

  On the other hand, when the shift range

  cement 50 is controlled so as to cause the

  smoothing of the displacer element 48 from the position of FIG. 3 so that the front projection 54 is brought to engage with the front recess 56 formed in the pinion 46 of small diameter on the drive shaft 35 , the displacement element 48 rotates integrally with the pinion 46 of small diameter, thereby transmitting the rotation of the pinion 64 of large diameter on the input shaft 57 towards the drive shaft 35, thereby causing the rota-

  tion of the drive disc 34 at a relative speed

  Consequently, in accordance with the above case in which the sub-transmission 38 is moved to the side of low speeds, the rotation of the drive disc 34 is transmitted to the drive wheels 25, 25 by marketing the

  tracks 24, 24 In this state in which the sub-

  transmission 38 maintained gear train b at high speed, snow removal tractor 1 can operate at a relatively high speed, which means that the movement on the high speed side of sub-transmission 38 is suitable when tractor 1 approaches or

  moves away from the snow disposal site.

  Incidentally, as shown in FIG. 1, the drive belts 19, 62 are each equipped respectively with a pair of safety systems comprising a pair of tensioners 67, 68 making it possible to keep the tension normal.

drive belts.

  Referring to FIG. 4, it can be seen that the security system which equips the drive belt 62 comprises a tension lever 66 which can rotate on its intermediate part on a dowel 65 secured to the chassis 2, the tension lever 66 having at the front end of a front branch 69 to which the tensioner 68 is rotatably attached and to the central part of the front branch 69 a spring 69 has connected at one of its ends to said branch and at its end on the chassis 2 in order to normally bias the tensioner 68 against the drive belt 62, a cable 72 connecting during operation, the rear end of the tension lever 68 to a hand lever 71 placed on the handle 70 of a snow removal tractor 1 When the hand lever 71 is driven downwards, the cable 72 is pulled by causing the tension lever 66 to rotate on the pin 65, thereby releasing the

  drive belt 62 of the tensioner contact-68.

  This condition corresponds to a functional stop state.

  operation of the tension lever 66 during which the speed change action of the sub-transmission 38 can take place favorably Especially, in this state, when the speed change operation is in progress, the shock of O in operation can avoid being transmitted to the shaft 7 of the motor 3, which allows

  a smoothly changing gear.

  As can be seen from the description above,

  according to the preferred embodiment of lin-

  vention, we provide a self-driving work vehicle

  powered in the form of a snow removal tractor in which the power transmission system from a motor to a driving wheel comprises a sub-transmission placed

  between an engine shaft and a main transmission

  friction disc type blade, which allows the operating speed to be suitably shifted to the low speed mode during

  the movement occurring during the work of elimination

  snow nation and towards high speed mode when moving away and coming closer

from the snow disposal site.

  In addition, with such an arrangement separate from the sub-transmission, the high-speed movement of the vehicle is carried out favorably without

  cause the diameter of the trans-

  known friction disc type mission which is

  inherently intended for the absorption of varia-

  couples This advantage clearly emerges from the arrangement described above in the sub-trans-

  mission 38 when we compare this one to the agency-

  known to the snow elimination tractor represented in FIG. 5 in which the power transmission system comprises a drive shaft 214 of supported drive disc

  to be mounted similarly.

  In addition, the above sub-transmission represents a simple structure as described above and can have a low cost price, which makes it possible to produce a vehicle of

  self-propelled work at a lower price.

  In addition, an increase in the range of reduction of the gear ratio of such a sub-transmission can allow the realization of a more compact model of a drive disc.

  as well as friction discs.

  In the above embodiment, the sub-transmission is presented in the form of a

  two-tree structure, while such a sub-

  transmission can be a triple shaft structure or a three-speed type or any

other suitable type.

  It also appears that in the embodiments of the invention, the tracks can

  be replaced with an ordinary pair of wheels.

  It is understood that the mode of realization

  sation described above is not limiting and that many modifications and variations may be made by technicians without departing either from the frame or the spirit

of the invention.

Claims (5)

  1 Self-propelled work vehicle (1) comprising a chassis (2), a motor (3) mounted on this chassis, a tool provided on the chassis, and connected to the motor to be driven by it, a walking mechanism suspended from the chassis of the vehicle, the drive mechanism having at least one drive wheel (25) mounted on an axle (27), a first transmission placed in the chassis, the first transmission having a drive shaft (14) s 'extending in a direction from the front to the rear of the vehicle,   a drive disc fixed in its center at the end   back of the drive shaft, a tree   drive (22) mounted on the rear of the drive disc   perpendicular to the drive shaft and   connected in operation to the axis of the drive wheel   and a friction disc (31) mounted so that it can slide on the driven shaft (32) in a non-rotatable manner and fixed on its periphery so as to be able to engage in friction with the drive disc, and a second transmission placed in the chassis of the vehicle, the second transmission being connected in operation to the engine and supporting at least the front end of the drive shaft, so that the drive power of the engine can be transmitted to the drive shaft in the form of a transmissible torque following the minus two gear ratios.   2 self-propelled work vehicle according to claim 1, characterized in that the working tool means comprise a helical auger (21) for collecting snow and a blower (23) for blowing snow both provided on the front part of the chassis. 2546454;   3 Self-propelled work vehicle according to claim 2, characterized in that the motor (3) comprises an output shaft mounted in a direction going from the front to the rear of the vehicle, and the second transmission means comprise- a housing supporting in rotation the front part of   the drive shaft (14) fixed on the drive disc   ment, an input shaft rotatably supporting and placed in said housing element in a direction from the front to the rear of the vehicle, the input shaft comprising at one of its ends an extension s' advancing outside the housing element and connected in operation to the motor output shaft, and transmission means for passing the drive torque of the input shaft between at least two gear ratios gears and transmit it in the form of a Training couple to the drive shaft.   4 Self-propelled work vehicle according to claim 3, characterized in that the transmission means comprise a first pinion of relatively small diameter and a second pinion of relatively large diameter both placed in said housing element, both fixed on the input shaft, and spaced apart from each other axially with respect to the input shaft, a third pinion of relatively large diameter and a fourth pinion of relatively small diameter, both placed in said housing element and both fixed and provided to be able to rotate without sliding along the drive shaft, so as to be constantly engaged respectively with the first pinion and with the second pinion, a spacer placed between the third pinion and the fourth pinion and fixed so as not to turn and slide along the drive shaft, a Make of recesses formed on each of the third pinions and fourth pinions on their respective sides facing the spacing element, and a pair of protrusions formed on both sides of the spacing element facing   the third and fourth gears respectively   tively, so as to form together with the recesses a pair of splashes.   5 Self-propelled work vehicle according to claim 1, characterized in that the vehicle displacement means comprise two -dl-drive wheels each connected to the two ends of the axle suspended from the vehicle chassis, and a pair of tracks (24) placed on each side of the chassis and   driven by each of the drive wheels.